CN113074818B - Method for rapidly acquiring indoor air temperature from outdoor through infrared thermal imaging - Google Patents
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Abstract
The invention provides a method for rapidly acquiring indoor air temperature from the outdoor through infrared thermal imaging, which comprises the following steps: acquiring environmental parameters of a building to which a room to be detected belongs and acquiring an infrared image of an external window hole of the room to be detected; if the opening degree of the windowing area in the acquired infrared image is larger than or equal to the opening degree set threshold value and the opening degree of the windowing area meets the resolution requirement of the infrared camera, calculating the indoor temperature by using the temperature of the windowing area, namely taking the temperature average value of the infrared temperature field of the windowing area in the infrared image as the indoor air temperature before windowing; and if the window in the obtained infrared image is completely closed and no obvious reflection phenomenon exists on the surface of the window glass, calculating the indoor air temperature by utilizing the temperature of the window which is effectively closed and based on the heat transfer model. The invention can utilize the infrared thermal imaging technology to obtain the indoor air temperature information through the outdoor window of the room, and realize the rapid and contactless accurate measurement of the indoor air temperature without entering the home.
Description
Technical Field
The invention belongs to the technical field of building energy-saving diagnosis, and particularly relates to a method for quickly acquiring indoor air temperature from the outdoors through infrared thermal imaging.
Background
For a central heating system in winter in northern areas, the indoor air temperature is an important index for evaluating the heating quality. Due to the unbalanced problem of the heating system, the phenomenon of overheating or supercooling often occurs in the user room, so that the indoor heating environment is uncomfortable. And when the temperature is too high, the user often adopts a windowing temperature reduction method, so that energy waste is further caused. At present, most room temperature monitoring equipment has the characteristics of difficult access to the home and high investment cost, so that the key for realizing the energy-saving diagnosis of the central heating system is to quickly and conveniently obtain the indoor air temperature information of the user. Infrared Thermography (IRT) is one of nondestructive technologies, and can observe the intensity distribution of Infrared radiation emitted by the surface of an object, and in the existing building energy audit, the Infrared Thermography technology is applied to quickly identifying defects related to structural characteristics, building materials and energy, such as a thermal bridge, an air leakage point, moisture permeation, heat preservation and shedding and the like, so that the problem solving efficiency is improved. However, the practical cases of applying the infrared thermal imaging technology in the field of central heating in China still limit the leakage detection of the heating pipeline, and the aspect of quick evaluation on the actual heating effect is still blank.
Disclosure of Invention
The invention aims to quickly acquire indoor temperature information from the outdoor in batch, provides a method for quickly acquiring indoor air temperature from the outdoor through infrared thermal imaging, and has the advantages of quickness and non-contact measurement. The invention applies the infrared thermal imaging technology to the indoor heat supply quality evaluation of the user for the first time, provides a method for quickly and conveniently obtaining the room temperature data of the user from the outdoor through the temperature information of the external window, and provides data support for the energy-saving diagnosis of a centralized heat supply system.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for rapidly acquiring indoor air temperature from the outdoor through infrared thermal imaging, which is characterized by comprising the following steps of:
1) acquiring environmental parameters of a building to which a room to be detected belongs and acquiring an infrared image of an external window hole of the room to be detected; wherein the environmental parameters include an ambient reflection temperature, an outdoor air temperature, and an outdoor wind speed;
2) judging whether each window meets the condition of calculating indoor temperature by utilizing the temperature of the window opening area
If the opening degree of the windowing area in the acquired infrared image is larger than or equal to the opening degree set threshold value and the opening degree of the windowing area meets the resolution requirement of the infrared camera, judging that the condition of calculating the indoor temperature by using the temperature of the windowing area is met, and executing the step 3);
if the window in the obtained infrared image is completely closed and no obvious light reflection phenomenon exists on the surface of the window glass, judging that the window is an effective window for closing the window, and executing the step 4);
if the conditions are not met, the temperature information of the window is invalid, and shooting is carried out again until any condition is met;
3) processing the acquired infrared image to obtain the temperature average value of the infrared temperature field of the windowing area in the infrared image, and taking the temperature average value as the indoor air temperature before windowing;
4) the method for calculating the indoor air temperature by utilizing the temperature of the window effectively closed comprises the following specific steps:
4.1) processing the obtained infrared image to obtain the average temperature value of the infrared temperature field of the window effectively closed in the infrared image; correcting the average value of the obtained effective window closing temperature according to the emissivity of the window and the environment reflection temperature and the outdoor air temperature obtained in the step 1) to obtain the outer surface temperature of the effective window closing window;
4.2) calculating the indoor air temperature according to the heat transfer model and outputting the indoor air temperature, and ending the method;
the calculation formula of the heat transfer model is as follows:
qconv，a-si＝qconv，se-amb+qrad，se-sky+qrad，se-gnd (1)
qconv，a-si＝Kwindow·(Ta-Tamb) (2)
qconv，se-amb＝hc·(Tsurf，ext-Tamb) (3)
qrad，se-sky＝0.5ε·σ·(Tsurf，ext 4-Tsky 4) (4)
qrad，se-gnd＝0.5ε·σ·(Tsurf，ext 4-Tground 4) (5)
hc＝0.365Vwind+4.967 (6)
Tskv＝Tamb-6 (7)
Tground＝0.89Tamb+2.25 (8)
in the formula:
qconv，a-sithe heat flow coefficient of convection heat transfer of indoor air to the inner surface of the outer window;
qconv，se-ambthe convection heat exchange heat flow coefficient of the outer surface of the outer window facing outdoor air;
qrad，se-skythe heat exchange heat flow coefficient of the long wave radiation facing the sky on the outer surface of the outer window is obtained;
qrad，se-gndthe heat flow coefficient of the long-wave radiation heat exchange is that the outer surface of the outer window faces the ground;
Tground，Tsky，Tamb，Tsurf，ext，Tathe temperature of the ground, the temperature of the sky, the temperature of outdoor air, the temperature of the outer surface of a window effectively closed and the temperature of indoor air are respectively set;
Vwindthe outdoor wind speed;
hcis the heat exchange coefficient of outdoor wall surface to flow, epsilon is the emissivity of single window outdoor surface, sigma is the Stefin Boltzmann constant, KwindowThe heat transfer coefficient of a single window;
the input parameters of the heat transfer model are as follows: the outdoor air temperature T obtained in the step 1)ambAnd outdoor wind speed VwindAnd 4.1) obtaining the temperature T of the outer surface of the window effectively closedsurf，extAnd window heat transfer coefficient Kwindow(ii) a The output parameters of the heat transfer model are as follows: indoor air temperature Ta。
The invention has the characteristics and beneficial effects that:
the infrared thermal imaging system has the technical characteristics of rapidness and no contact, and the infrared thermal imaging technology can rapidly acquire the indoor temperature distribution condition of each household from the outdoor. The invention applies the infrared thermal imaging technology to the outdoor acquisition of the indoor air temperature for the first time, and provides a method for acquiring the indoor air temperature information through a user external window (both windowing and non-windowing are applicable) by utilizing the infrared thermal imaging technology. Therefore, the indoor air temperature can be measured quickly and accurately without contact under the condition of not needing to enter a house.
The beneficial effects brought by the technical characteristics comprise: the method is simple to operate, the time is shortened, the manpower and material resources are saved, and the indoor air temperature information can be obtained through the infrared image without entering a house; furthermore, the room temperature difference of different residents can be presented through the infrared image of the outer facade of the building, so that the space-time distribution characteristic of the room temperature is rapidly grasped, the rapid evaluation of the centralized heating effect is realized, and data support is provided for the energy-saving diagnosis of the centralized heating system.
Drawings
FIG. 1 is an overall flow chart of a method for rapidly acquiring indoor air temperature from outdoors by infrared thermal imaging according to the present invention;
fig. 2 is a schematic diagram of a heat transfer model employed in an embodiment of the present invention.
FIG. 3 is a schematic diagram of an experiment conducted to verify the effectiveness of the present invention.
Fig. 4 is an infrared image of a building facade measured at 8 different window openings.
FIG. 5 is a graph of experimental temperature data from experiments conducted to verify the effectiveness of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the detailed description and specific examples, while indicating the scope of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
For better understanding of the present invention, an application example of a method for rapidly acquiring indoor air temperature from the outdoors by infrared thermal imaging proposed by the present invention is explained in detail below.
Referring to fig. 1, a method for rapidly acquiring indoor air temperature from the outdoors through infrared thermal imaging according to the present invention comprises the steps of:
1) the method comprises the steps of obtaining environmental parameters of a building to which a room to be measured belongs and obtaining an infrared image of an external window hole of the room to be measured, wherein the environmental parameters and the infrared image are obtained under the condition of no direct solar radiation (such as at night or in cloudy days) in order to avoid the direct solar radiation from influencing a measurement result. The method comprises the following specific steps:
1.1) obtaining the environmental parameters of the building to which the room to be tested belongs
The method comprises the following steps of obtaining environmental parameters of a building to which a tested room belongs, including environment reflection temperature, outdoor air temperature and outdoor wind speed, and the specific process comprises the following steps:
a piece of crumpled aluminum foil paper is unfolded and pasted on the building outer vertical surface of a room to be detected, the radiance is set to be 1.0 on an infrared camera, an infrared image of the aluminum foil paper is shot, the infrared temperature of the aluminum foil paper is directly read on the infrared camera, the value is the ambient reflection temperature, and the ambient reflection temperature is set on the infrared camera. And measuring the outdoor air temperature by using a temperature sensor, and setting the outdoor air temperature on the infrared camera after reading the value. The outdoor wind speed was measured with an anemometer for subsequent heat transfer model construction.
1.2) obtaining the infrared image of the window hole of the outer window of the room to be detected
Taking the window hole of the outer window of the room, which is required to acquire the indoor temperature, on the outer facade without the shielding of the building as a shooting object (the shooting object can be the outer window holes of a plurality of rooms); setting a proper shooting distance (less than 10 meters) on the infrared camera to ensure that the head-up shooting can obtain a clear and complete infrared image of a shooting object; setting emissivity on the infrared camera, wherein the suggested value range is 0.9-0.97; and acquiring an infrared image of the photographic object by using the infrared camera at the set photographing distance and emissivity.
2) Judging whether each window meets the condition of calculating indoor temperature by using window opening area temperature
If the opening degree of the window opening area in the acquired infrared image is greater than or equal to the opening degree setting threshold (the opening degree setting threshold is 35% in the embodiment), and the opening degree area of the window opening area meets the resolution requirement of the infrared camera and meets the accuracy of subsequent infrared temperature field calculation, it is determined that the condition of calculating the indoor temperature by using the temperature of the window opening area is met, and step 3 is executed.
And if the window in the acquired infrared image is completely closed and no obvious light reflection phenomenon exists on the surface of the window glass (namely the temperature field on the surface of the window glass is uniform), judging that the window is an effective window for closing the window, and executing the step 4).
If the conditions are not met (for example, the opening degree of a window opening area in the acquired infrared image is smaller than an opening degree set threshold value, or an obvious light reflection phenomenon exists on the surface of window glass), the temperature information of the window is invalid, and shooting is carried out again until any condition is met.
3) Calculating indoor air temperature using temperature of windowed area
The obtained infrared image is input to infrared image processing software (in this embodiment, image processing software of an infrared camera is used), and a temperature average value of an infrared temperature field of a windowed area in the infrared image is obtained.
Under the condition of windowing, the average temperature value of the infrared temperature field of the windowing region (the calculated temperature of the windowing window) corresponds to the temperature of the inner wall opposite to the window, and under the condition that the indoor thermal environment is stable, the temperature of the inner wall is approximately consistent with the temperature of the indoor air before windowing, the obtained average temperature value of the infrared temperature field of the windowing region is used as the temperature of the indoor air before windowing, and the error is within +/-1K.
4) Calculating indoor air temperature using temperature of effectively closed window
4.1) obtaining the average temperature value of the window effectively closed
The acquired infrared image is input into infrared image processing software (in this embodiment, image processing software of an infrared camera is used), and a temperature average value of an infrared temperature field of a window effectively closed in the infrared image is obtained.
The emissivity epsilon and the heat transfer coefficient K of the window were selected according to Table 1windowAnd correcting the average value of the obtained effective window closing temperature according to the emissivity of the window and the environment reflection temperature and the outdoor air temperature obtained in the step 1) to obtain the outer surface temperature of the effective window closing window.
TABLE 1 exterior Window emissivity and Heat transfer coefficient query
4.2) calculating the indoor air temperature according to the heat transfer model
Principle schematic diagram of heat transfer model referring to fig. 2, after the heat transfer coefficient of a window is selected, the indoor air temperature can be calculated through the heat transfer model according to the outer surface temperature of the window effectively closed.
The heat transfer model is constructed by using simulation software (such as MATLAB, EES, MODELICA and the like), and the specific formula of the heat transfer model is as follows:
qconv，a-si＝qconv，se-amb+qrad，se-sky+qrad，se-gnd (1)
qconv，a-si＝Kwindow·(Ta-Tamb) (2)
qconv，se-amb＝hc·(Tsurf，ext-Tamb) (3)
qrad，se-sky＝0.5ε·σ·(Tsurf，ext 4-Tsky 4) (4)
qrad，se-gnd＝0.5ε·σ·(Tsurf，ext 4-Tground 4) (5)
hc＝0.365Vwind+4.967 (6)
Tskv＝Tamb-6 (7)
Tground＝0.89Tamb+2.25 (8)
in the formula:
qconv，a-sithe heat flow coefficient of convection heat transfer of indoor air to the inner surface of the outer window;
qconv，se-ambthe convection heat exchange heat flow coefficient of the outer surface of the outer window facing outdoor air;
qrad，se-skythe heat exchange heat flow coefficient of the long wave radiation facing the sky on the outer surface of the outer window is obtained;
qrad，se-gndthe heat flow coefficient of the long-wave radiation heat exchange is that the outer surface of the outer window faces the ground;
Tground，Tsky，Tamb，Tsurf，extand TaSequentially setting ground temperature, sky temperature, outdoor air temperature, effective window closing outer surface temperature and indoor air temperature;
Vwindthe outdoor wind speed;
hcis the heat exchange coefficient of the outdoor wall surface to the flow, epsilon is the emissivity of the outer surface of the outer window, sigma is the Stefin Boltzmann constant, and the value is 5.67-10-8，KwindowThe heat transfer coefficient of a single window.
The input parameters of the heat transfer model are: outdoor air temperature TambOutdoor wind speed VwindEffectively closing the outer surface temperature T of the windowsurf，extAnd window heat transfer coefficient Kwindow. Wherein the outdoor air temperature TambAnd outdoor wind speed VwindObtaining the temperature T of the outer surface of the effective closed window by the step 1.1)surf，extThe heat transfer coefficient K of the single window obtained in the step 4.1)windowIn step 4.1) according to the table 1. Through heat transfer model simulation, the parameter T is finally outputaNamely the indoor air temperature value, and the method is finished.
Further, the specific value of each set value in the invention needs to consider the environmental parameters of the environment where the building is located, the tolerance rate of the method of the invention and other factors.
The effectiveness of the method of the invention is verified experimentally as follows:
in order to verify the relevance between the infrared thermal imaging temperature acquired by a windowing region and the actually measured indoor air temperature before windowing under the condition of windowing, the accuracy of shooting at different window openings is experimentally verified under the heat supply working condition of an experimental room, and the measurement precision and feasibility of the method are analyzed.
As shown in figure 4, the room used in the experiment has the size of 3m multiplied by 3m, the heat supply tail end of the room is provided with a fan coil, indoor air temperature and inner wall surface temperature measuring points are arranged in the room, outdoor air temperature monitoring points are arranged outdoors, and various temperature sensors adopt thermal resistors Pt 100. Crumpled aluminum foil paper is pasted on the outer wall beside the outer window hole to assist in obtaining the outdoor environment reflection temperature in the follow-up process.
Considering that the temperature at the outer window hole should be related to the indoor air temperature and the temperature of the inner wall surface, 8 different window openings (5%, 10%, 15%, 20%, 35%, 50%, 75% and 100%, respectively) were selected for rapid photographing of the outer facade of the wall. In the process of image processing, the ambient reflection temperature changes along with the change of the outdoor air temperature, so that the ambient reflection temperature is corrected in real time each time an infrared image is processed. The obtained infrared temperature is compared with the actual measurement value of the temperature sensor, and the experimental results and the corresponding data tables are shown in fig. 5 and table 2.
TABLE 2 windowing experiment data sheet
By analyzing the graph, it can be seen that:
1) when heat is supplied in winter, the indoor air temperature before windowing can better reflect the indoor environment condition of heat supply in winter, but the indoor air temperature after windowing is rapidly reduced, the condition of indoor overheating cannot be truly reflected, and the temperature of an inner wall is relatively stable; when the opening degree of the window is larger than 35%, the infrared temperature value obtained through the windowing area approaches to the temperature value of the inner wall opposite to the window, and the absolute value of the error between the infrared temperature and the actually measured inner wall temperature is smaller than 0.5K. Further, when the opening degree of the window is larger than 35%, the absolute value of the error between the infrared temperature and the air temperature before windowing (opening degree of 0%) is smaller than 1K.
2) Under the condition of long-time room heating, the temperature of the inner wall is very close to the air temperature, so that the infrared test temperature obtained by the method can accurately reflect the air temperature value before windowing, and the error is within +/-1K.
3) The method can quickly and conveniently acquire the indoor air temperature information of the user from the outdoor, and the error range is within +/-1K, so that the method has higher feasibility in acquiring the indoor air temperature by utilizing the infrared thermal imaging technology.
In summary, the invention applies the infrared thermal imaging technology to the indoor heat supply quality assessment of the user for the first time, provides a method for rapidly and contactlessly obtaining the room temperature data of the user from the outdoor through window information, and provides data support for the energy-saving diagnosis of the central heating system.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (3)
1. A method for rapidly acquiring indoor air temperature from the outdoor through infrared thermal imaging is characterized by comprising the following steps:
1) acquiring environmental parameters of a building to which a room to be detected belongs and acquiring an infrared image of an external window hole of the room to be detected; wherein the environmental parameters include an ambient reflection temperature, an outdoor air temperature, and an outdoor wind speed;
2) judging whether each window meets the condition of calculating indoor temperature by utilizing the temperature of the window opening area
If the opening degree of the windowing area in the acquired infrared image is larger than or equal to the opening degree set threshold value and the opening degree of the windowing area meets the resolution requirement of the infrared camera, judging that the condition of calculating the indoor temperature by using the temperature of the windowing area is met, and executing the step 3);
if the window in the obtained infrared image is completely closed and no obvious light reflection phenomenon exists on the surface of the window glass, the window is judged to be an effective window closing window, the condition that the indoor temperature is calculated by utilizing the temperature of the effective window closing window is judged to be met, and the step 4) is executed;
if the conditions are not met, the temperature information of the window is invalid, and shooting is carried out again until any condition is met;
3) processing the acquired infrared image to obtain the temperature average value of the infrared temperature field of the windowing area in the infrared image, and taking the temperature average value as the indoor air temperature before windowing;
4) the method for calculating the indoor air temperature by utilizing the temperature of the window effectively closed comprises the following specific steps:
4.1) processing the obtained infrared image to obtain the average temperature value of the infrared temperature field of the window effectively closed in the infrared image; correcting the average value of the obtained effective window closing temperature according to the emissivity of the window and the environment reflection temperature and the outdoor air temperature obtained in the step 1) to obtain the outer surface temperature of the effective window closing;
4.2) calculating the indoor air temperature according to the heat transfer model and outputting the indoor air temperature, and ending the method;
the calculation formula of the heat transfer model is as follows:
qconv，a-si＝qconv，se-amb+qrad，se-sky+qrad，se-gnd (1)
qconv，a-si＝Kwindow·(Ta-Tamb) (2)
qconv，se-amb＝hc·(Tsurf，ext-Tamb) (3)
qrad，se-sky＝0.5ε·σ·(Tsurf，ext 4-Tsky 4) (4)
qrad，se-gnd＝0.5ε·σ·(Tsurf，ext 4-Tground 4) (5)
hc＝0.365Vwind+4.967 (6)
Tsky＝Tamb-6 (7)
Tground＝0.89Tamb+2.25 (8)
in the formula:
qconv，a-sithe heat flow coefficient of convection heat transfer of indoor air to the inner surface of the outer window;
qconv，se-ambthe convection heat exchange heat flow coefficient of the outer surface of the outer window facing outdoor air;
qrad，se-skythe heat exchange heat flow coefficient of the long wave radiation facing the sky on the outer surface of the outer window is obtained;
qrad，se-gndthe heat flow coefficient of the long-wave radiation heat exchange is that the outer surface of the outer window faces the ground;
Tground，Tsky，Tamb，Tsurf，ext，Tathe temperature of the ground, the temperature of the sky, the temperature of outdoor air, the temperature of the outer surface of a window effectively closed and the temperature of indoor air are respectively set;
Vwindthe outdoor wind speed;
hcis the heat exchange coefficient of outdoor wall surface to flow, epsilon is the emissivity of single window outdoor surface, sigma is the Stefin Boltzmann constant, KwindowThe heat transfer coefficient of a single window;
the input parameters of the heat transfer model are as follows: the outdoor air temperature T obtained in the step 1)ambAnd outdoor wind speed VwindAnd 4.1) obtaining the temperature T of the outer surface of the window effectively closedsurf，extAnd window heat transfer coefficient Kwindow(ii) a The output parameters of the heat transfer model are as follows: indoor air temperature Ta。
2. The method according to claim 1, wherein in step 1), the environmental parameter and the infrared image are both acquired without direct sunlight.
3. The method according to claim 1 or 2, wherein in step 2), the opening setting threshold is set to 35%.
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| US9121760B2 (en) * | 2010-01-27 | 2015-09-01 | Ci Systems Ltd. | Room-temperature filtering for passive infrared imaging |
| WO2014185033A1 (en) * | 2013-05-17 | 2014-11-20 | パナソニック インテレクチュアル プロパティ コーポレーション オブ アメリカ | Thermal image sensor and user interface |
| CN106610316B (en) * | 2016-12-29 | 2019-04-30 | 重庆工商大学 | Thin-walled Local Condensing Heat Transfer Coefficients measurement method based on heat fluctuation coupling infrared imaging |
| CN106969838B (en) * | 2017-05-31 | 2019-06-25 | 孔文欣 | Heating system user's dehydration detection method based on infrared thermal imagery |
| CN112097916B (en) * | 2020-09-15 | 2022-07-08 | 周清峰 | Medical epidemic prevention temperature measurement system and method |
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